Indiana Rep. Luke Messer speaks at a rally outside the Supreme Court on Jan. 11, 2015, as the court heard arguments in a case involving 10 California teachers who said they had a First Amendment right not to pay fees to a union. (Bill Clark/CQ Roll Call file photo)

The Supreme Court appears set to overturn a decades-old precedent and deal a financial blow to Democratic-aligned unions that represent teachers and other public-sector employees in a major case with blatant political overtones.

Ahead of oral arguments Monday, two Democratic senators sent the justices this message: The Supreme Court’s reputation is at stake, and overturning the 1977 ruling will further erode the public’s confidence that the federal courts are neutral and above politics.

Sens. Sheldon Whitehouse of Rhode Island and Richard Blumenthal of Connecticut filed a brief that argues the justices should follow what’s known as stare decisis, a principle of American courts that gives respect to prior rulings.

“If stare decisis means anything, it must mean that a precedent should not be overturned simply because a differently composed court emerges,” the senators wrote. “Decision-making begins to look like prize-taking when precedents are reversed as Court majorities shift.”

The case asks the Supreme Court to overturn an opinion that allows public-sector unions to collect fees from nonmembers to cover the union’s cost for actions that help all employees. The challenger, Illinois state employee Mark Janus, argues the fees are coerced speech that violate his First Amendment rights.

Legal experts predict that President Donald Trump’s appointment of Justice Neil Gorsuch last year, which filled the vacancy left by Antonin Scalia’s death in 2016, all but ensured a ruling against the unions.

And that’s what conservative lawmakers expect, too. Senate Majority Leader Mitch McConnell told The New York Times earlier this month that the case is “an example” of why he found it important to block President Barack Obama from replacing the consistently conservative Scalia — and that a ruling against unions could have an impact on Democratic fundraising.

Revisited issue

The conservative wing of the court has already shown a willingness to overturn Abood v. Detroit Board of Education, the 1977 decision that has allowed unions to avoid “free rider” public employees who get the benefits of a union’s work without paying any dues.

Unions and outside experts say more free riders would mean less money for the core functions of collective bargaining, and less money for campaign donations. Unions would have to shift remaining funds to the costs of bargaining for all members — and that would overwhelmingly hurt the Democratic Party and its candidates, the benefactors of the vast majority of union political donations.

In a 2014 decision, Harris v. Quinn, a 5-4 majority found that home care workers in Illinois can’t be forced to pay union dues. In the opinion, Justice Samuel A. Alito Jr. called the legal reasoning behind Abood “questionable on several grounds.”

Scalia had appeared ready to cast a vote to overturn Abood before his death in a case called Friedrichs v. California Teachers Association. Instead, the shorthanded court deadlocked at 4-4 in 2016, which affirmed a lower court order that kept Abood intact.

Gorsuch’s legal approach follows Scalia’s.

A case of politics

Whitehouse and Blumenthal, in their brief, argue that the case is part of a broader special-interest campaign spanning multiple cases brought only to overturn Abood. The Friedrichs case was underwritten by the Lynde and Harry Bradley Foundation, which has acknowledged its goal of reducing the size and power of public sector unions. The private, grant-making organization based in Milwaukee funds numerous conservative causes.

The senators wrote that this case, brought by “well-heeled interests,” is an example of “sophisticated and powerful interests” that “appear in droves to enlist federal courts as their agents in political contests.”

And they highlight how Chief Justice John G. Roberts Jr., in a case about partisan gerrymandering, expressed concern about what the “intelligent man on the street” would think of the court’s “status and integrity” if it were to continually adjudicate political disputes.

The background of the case means that the court needs to be vigilant of its apolitical role, Whitehouse and Blumenthal wrote.

“Otherwise, the ‘intelligent man’ will reach only one conclusion: that the Court is being asked to reach a political decision because the interests involved in that campaign think — and have telegraphed and telegraphed and telegraphed — that, based on this Court’s changed membership, a 5-4 victory awaits them,” the senators’ brief states.